Some electroacoustic transducers of earphones and headphones are condenser type electroacoustic transducers that have excellent frequency response and are suitable for high fidelity (Hi-Fi) playback. In general, condenser type electroacoustic transducers are of a push-pull scheme that can reduce harmonic distortion. A condenser type electroacoustic transducer includes a diaphragm and a pair of fixed electrodes facing the respective faces of the diaphragm.
With respect to earphones including condenser type electroacoustic transducers, closed type earphones (for example, refer to PTL 1) and open type earphones (refer to NPL 1) have been proposed.